Changeset 7ef162b2 for libcfa/src/concurrency

Timestamp:

Nov 22, 2021, 1:07:05 PM (2 years ago)

Author:

Thierry Delisle <tdelisle@…>

Branches:

ADT, ast-experimental, enum, forall-pointer-decay, master, pthread-emulation, qualifiedEnum

Children:

6ddef36, ddd2ec9

Parents:

059ad16

Message:

First attempt at using io_uring_enter for idle sleep.

Location:

libcfa/src/concurrency

Files:

• io.cfa (modified) (4 diffs)
• io/setup.cfa (modified) (1 diff)
• io/types.hfa (modified) (1 diff)
• kernel.cfa (modified) (9 diffs)

libcfa/src/concurrency/io.cfa

@@ -173 +173 @@
 
                 ctx.proc->io.pending = false;
-
-                return __cfa_io_drain( proc );
+                ready_schedule_lock();
+                bool ret = __cfa_io_drain( proc );
+                ready_schedule_unlock();
+                return ret;
         }
 
@@ -278 +280 @@
         }
 
-
         //=============================================================================================
         // submission
@@ -301 +302 @@
                 ctx->proc->io.dirty   = true;
                 if(sq.to_submit > 30 || !lazy) {
-                        ready_schedule_lock();
                         __cfa_io_flush( ctx->proc, false );
-                        ready_schedule_unlock();
                 }
         }
@@ -502 +501 @@
                 }
         }
+
+        bool __kernel_read(processor * proc, io_future_t & future, char buf[], int fd) {
+                $io_context * ctx = proc->io.ctx;
+                /* paranoid */ verify( ! __preemption_enabled() );
+                /* paranoid */ verify( proc == __cfaabi_tls.this_processor );
+                /* paranoid */ verify( ctx );
+
+                __u32 idx;
+                struct io_uring_sqe * sqe;
+
+                // We can proceed to the fast path
+                if( !__alloc(ctx, &idx, 1) ) return false;
+
+                // Allocation was successful
+                __fill( &sqe, 1, &idx, ctx );
+
+                sqe->opcode = IORING_OP_READ;
+                sqe->user_data = (uintptr_t)&future;
+                sqe->flags = 0;
+                sqe->ioprio = 0;
+                sqe->fd = 0;
+                sqe->off = 0;
+                sqe->fsync_flags = 0;
+                sqe->__pad2[0] = 0;
+                sqe->__pad2[1] = 0;
+                sqe->__pad2[2] = 0;
+                sqe->addr = (uintptr_t)buf;
+                sqe->len = sizeof(uint64_t);
+
+                asm volatile("": : :"memory");
+
+                /* paranoid */ verify( sqe->user_data == (uintptr_t)&future );
+                __submit( ctx, &idx, 1, true );
+
+                /* paranoid */ verify( proc == __cfaabi_tls.this_processor );
+                /* paranoid */ verify( ! __preemption_enabled() );
+        }
 #endif

libcfa/src/concurrency/io/setup.cfa

@@ -220 +220 @@
                 cq.cqes = (struct io_uring_cqe *)(((intptr_t)cq.ring_ptr) + params.cq_off.cqes);
 
-                // Step 4 : eventfd
-                // io_uring_register is so f*cking slow on some machine that it
-                // will never succeed if preemption isn't hard blocked
-                __cfadbg_print_safe(io_core, "Kernel I/O : registering %d for completion with ring %d\n", procfd, fd);
-
-                __disable_interrupts_hard();
-
-                int ret = syscall( __NR_io_uring_register, fd, IORING_REGISTER_EVENTFD, &procfd, 1);
-                if (ret < 0) {
-                        abort("KERNEL ERROR: IO_URING EVENTFD REGISTER - %s\n", strerror(errno));
-                }
-
-                __enable_interrupts_hard();
-
-                __cfadbg_print_safe(io_core, "Kernel I/O : registered %d for completion with ring %d\n", procfd, fd);
+                #if !defined(IO_URING_IDLE)
+                        // Step 4 : eventfd
+                        // io_uring_register is so f*cking slow on some machine that it
+                        // will never succeed if preemption isn't hard blocked
+                        __cfadbg_print_safe(io_core, "Kernel I/O : registering %d for completion with ring %d\n", procfd, fd);
+
+                        __disable_interrupts_hard();
+
+                        int ret = syscall( __NR_io_uring_register, fd, IORING_REGISTER_EVENTFD, &procfd, 1);
+                        if (ret < 0) {
+                                abort("KERNEL ERROR: IO_URING EVENTFD REGISTER - %s\n", strerror(errno));
+                        }
+
+                        __enable_interrupts_hard();
+
+                        __cfadbg_print_safe(io_core, "Kernel I/O : registered %d for completion with ring %d\n", procfd, fd);
+                #endif
 
                 // some paranoid checks

libcfa/src/concurrency/io/types.hfa

@@ -185 +185 @@
 
         // Wait for the future to be fulfilled
-        bool wait( io_future_t & this ) {
-                return wait(this.self);
-        }
-
-        void reset( io_future_t & this ) {
-                return reset(this.self);
-        }
+        bool wait     ( io_future_t & this ) { return wait     (this.self); }
+        void reset    ( io_future_t & this ) { return reset    (this.self); }
+        bool available( io_future_t & this ) { return available(this.self); }
 }

libcfa/src/concurrency/kernel.cfa

@@ -34 +34 @@
 #include "strstream.hfa"
 #include "device/cpu.hfa"
+#include "io/types.hfa"
 
 //Private includes
@@ -124 +125 @@
 static void __wake_one(cluster * cltr);
 
-static void idle_sleep(processor * proc);
+static void idle_sleep(processor * proc, io_future_t & future, char buf[]);
 static bool mark_idle (__cluster_proc_list & idles, processor & proc);
 static void mark_awake(__cluster_proc_list & idles, processor & proc);
@@ -134 +135 @@
 static inline bool __maybe_io_drain( processor * );
 
+extern bool __kernel_read(processor * proc, io_future_t & future, char buf[], int fd);
+
 extern void __disable_interrupts_hard();
 extern void __enable_interrupts_hard();
@@ -148 +151 @@
         /* paranoid */ verify( __preemption_enabled() );
 }
+
 
 //=============================================================================================
@@ -163 +167 @@
         verify(this);
 
+        io_future_t future; // used for idle sleep when io_uring is present
+        future.self.ptr = 1p;  // mark it as already fulfilled so we know if there is a pending request or not
+        char buf[sizeof(uint64_t)];
+
         __cfa_io_start( this );
 
@@ -196 +204 @@
 
                         if( !readyThread ) {
-                                ready_schedule_lock();
                                 __cfa_io_flush( this, false );
-                                ready_schedule_unlock();
 
                                 readyThread = __next_thread_slow( this->cltr );
@@ -229 +235 @@
                                 }
 
-                                idle_sleep( this );
+                                idle_sleep( this, future, buf );
 
                                 // We were woken up, remove self from idle
@@ -250 +256 @@
 
                         if(this->io.pending && !this->io.dirty) {
-                                ready_schedule_lock();
                                 __cfa_io_flush( this, false );
-                                ready_schedule_unlock();
                         }
 
@@ -773 +777 @@
 }
 
-static void idle_sleep(processor * this) {
-        #if !defined(__CFA_NO_STATISTICS__)
-                if(this->print_halts) {
-                        __cfaabi_bits_print_safe( STDOUT_FILENO, "PH:%d - %lld 0\n", this->unique_id, rdtscl());
-                }
-        #endif
-
-        __cfadbg_print_safe(runtime_core, "Kernel : core %p waiting on eventfd %d\n", this, this->idle_fd);
-
-        {
-                eventfd_t val;
-                ssize_t ret = read( this->idle_fd, &val, sizeof(val) );
-                if(ret < 0) {
-                        switch((int)errno) {
-                        case EAGAIN:
-                        #if EAGAIN != EWOULDBLOCK
-                                case EWOULDBLOCK:
-                        #endif
-                        case EINTR:
-                                // No need to do anything special here, just assume it's a legitimate wake-up
-                                break;
-                        default:
-                                abort( "KERNEL : internal error, read failure on idle eventfd, error(%d) %s.", (int)errno, strerror( (int)errno ) );
+static void idle_sleep(processor * this, io_future_t & future, char buf[]) {
+        #if !defined(IO_URING_IDLE) || !defined(CFA_HAVE_LINUX_IO_URING_H)
+                #if !defined(__CFA_NO_STATISTICS__)
+                        if(this->print_halts) {
+                                __cfaabi_bits_print_safe( STDOUT_FILENO, "PH:%d - %lld 0\n", this->unique_id, rdtscl());
                         }
-                }
-        }
-
-        #if !defined(__CFA_NO_STATISTICS__)
-                if(this->print_halts) {
-                        __cfaabi_bits_print_safe( STDOUT_FILENO, "PH:%d - %lld 1\n", this->unique_id, rdtscl());
-                }
+                #endif
+
+                __cfadbg_print_safe(runtime_core, "Kernel : core %p waiting on eventfd %d\n", this, this->idle_fd);
+
+                {
+                        eventfd_t val;
+                        ssize_t ret = read( this->idle_fd, &val, sizeof(val) );
+                        if(ret < 0) {
+                                switch((int)errno) {
+                                case EAGAIN:
+                                #if EAGAIN != EWOULDBLOCK
+                                        case EWOULDBLOCK:
+                                #endif
+                                case EINTR:
+                                        // No need to do anything special here, just assume it's a legitimate wake-up
+                                        break;
+                                default:
+                                        abort( "KERNEL : internal error, read failure on idle eventfd, error(%d) %s.", (int)errno, strerror( (int)errno ) );
+                                }
+                        }
+                }
+
+                #if !defined(__CFA_NO_STATISTICS__)
+                        if(this->print_halts) {
+                                __cfaabi_bits_print_safe( STDOUT_FILENO, "PH:%d - %lld 1\n", this->unique_id, rdtscl());
+                        }
+                #endif
+        #else
+                #if !defined(CFA_HAVE_IORING_OP_READ)
+                        #error this is only implemented if the read is present
+                #endif
+                // Do we already have a pending read
+                if(available(future)) {
+                        // There is no pending read, we need to add one
+                        reset(future);
+
+                        __kernel_read(this, future, buf, this->idle_fd );
+                }
+
+                __cfa_io_flush( this, true );
         #endif
 }